Buggy code:
public class SefConnectionProxy implements Connection { private SefDataSourceProxy owner ; private final Connection to ; protected int connId ; public SefConnectionProxy ( SefDataSourceProxy owner , Connection to ) { } public SefConnectionProxy ( SefDataSourceProxy owner , Connection to , int connId ) { } public SefDataSourceProxy getOwner ( ) { } public Connection getUnderlyingConnection ( ) { } public int getUnderlyingConnectionId ( ) { } public void onChildStatementClose ( SefStatementProxy statement ) { } public void close ( ) throws SQLException { } public boolean isClosed ( ) throws SQLException { } public Statement createStatement ( ) throws SQLException { } public PreparedStatement prepareStatement ( String sql ) throws SQLException { } public CallableStatement prepareCall ( String sql ) throws SQLException { } public Statement createStatement ( int resultSetType , int resultSetConcurrency ) throws SQLException { } public PreparedStatement prepareStatement ( String sql , int resultSetType , int resultSetConcurrency ) throws SQLException { } public CallableStatement prepareCall ( String sql , int resultSetType , int resultSetConcurrency ) throws SQLException { } public Statement createStatement ( int resultSetType , int resultSetConcurrency , int resultSetHoldability ) throws SQLException { } public CallableStatement prepareCall ( String sql , int resultSetType , int resultSetConcurrency , int resultSetHoldability ) throws SQLException { } public PreparedStatement prepareStatement ( String sql , int autoGeneratedKeys ) throws SQLException { } public PreparedStatement prepareStatement ( String sql , int resultSetType , int resultSetConcurrency , int resultSetHoldability ) throws SQLException { } public PreparedStatement prepareStatement ( String sql , int [ ] columnIndexes ) throws SQLException { } public PreparedStatement prepareStatement ( String sql , String [ ] columnNames ) throws SQLException { } public String nativeSQL ( String sql ) throws SQLException { } public void setAutoCommit ( boolean autoCommit ) throws SQLException { } public boolean getAutoCommit ( ) throws SQLException { } public void setTransactionIsolation ( int level ) throws SQLException { } public int getTransactionIsolation ( ) throws SQLException { } public void commit ( ) throws SQLException { } public void rollback ( ) throws SQLException { } public void releaseSavepoint ( Savepoint savepoint ) throws SQLException { } public void rollback ( Savepoint savepoint ) throws SQLException { } public Savepoint setSavepoint ( ) throws SQLException { } public Savepoint setSavepoint ( String name ) throws SQLException { } public void abort ( Executor executor ) throws SQLException { } public void setReadOnly ( boolean readOnly ) throws SQLException { } public boolean isReadOnly ( ) throws SQLException { } public int getHoldability ( ) throws SQLException { } public void setHoldability ( int holdability ) throws SQLException { } public DatabaseMetaData getMetaData ( ) throws SQLException { } public void setCatalog ( String catalog ) throws SQLException { } public String getCatalog ( ) throws SQLException { } public SQLWarning getWarnings ( ) throws SQLException { } public void clearWarnings ( ) throws SQLException { } @ SuppressWarnings ( { "rawtypes" , "unchecked" } ) public Map getTypeMap ( ) throws SQLException { } public void setTypeMap ( Map < String , Class < ? > > map ) throws SQLException { } public Array createArrayOf ( String typeName , Object [ ] elements ) throws SQLException { } public Blob createBlob ( ) throws SQLException { } public Clob createClob ( ) throws SQLException { } public NClob createNClob ( ) throws SQLException { } public SQLXML createSQLXML ( ) throws SQLException { } public Struct createStruct ( String typeName , Object [ ] attributes ) throws SQLException { } public Properties getClientInfo ( ) throws SQLException { } public String getClientInfo ( String name ) throws SQLException { } public void setClientInfo ( Properties properties ) throws SQLClientInfoException { } public void setClientInfo ( String name , String value ) throws SQLClientInfoException { } public boolean isValid ( int timeout ) throws SQLException { <START_BUG> return isValid ( timeout ) ; <END_BUG> } public boolean isWrapperFor ( Class < ? > iface ) throws SQLException { } public < T > T unwrap ( Class < T > iface ) throws SQLException { } public void setSchema ( String schema ) throws SQLException { } public String getSchema ( ) throws SQLException { } public void setNetworkTimeout ( Executor executor , int milliseconds ) throws SQLException { } public int getNetworkTimeout ( ) throws SQLException { } @ Override public boolean equals ( Object obj ) { } @ Override public String toString ( ) { } }

Fix:
return to . isValid ( timeout ) ;